Friction clutch

ABSTRACT

An improved dry-disc friction clutch for motor vehicle power transmission systems is disclosed, which is adapted to be disengaged completely and immediately when a forward drive condition is to be established from idling. The friction clutch includes a flywheel which is made up of cooperating main and subsidiary driving plates which are normally spaced from each other by suitable spring means. The subsidiary driving plate is positively moved away from the friction-engaging plate when the clutch pedal is depressed and the clutch spring is moved to disengage the pressure plate from the friction-engaging plate.

United States Patent 1 Shono FRICTION CLUTCH [75] Inventor:

[73] Assigneez Nissan Motor Company, Limited,

' Yokohama, Japan 22 Filed: Dec. 20, 1971 [21] App]. No.: 209,757.

Kinji Shono, Wakoh, Japan [30] Foreign Application'lriority Data Dec.28, 1970 Japan 45/132196 [52] U.S. Cl. 192/70.27', 192/89 B [51] Int.Cl. Fl6d 13/44 [58] Field of Search 192/70.27, 70.28,

[56] References Cited UNITED STATES PATENTS 2,090,265 8/1937 Padgett[92/7027 X 2,630,897 3/1953 Porter 2,700,444 l/1955 Ahlen 192/89 B June19, 1973 FOREIGN PATENTS OR APPLICATIONS 1,027,999 4/1958 Germany [92/89B Primary Etarqinep-Allan D. Herrmann A tt0rney-Robert E. Burns andEmmanuel .I. Lobato [57] ABSTRACT An improved dry-disc friction clutchfor motor vehicle power transmission systems is disclosed, which isadapted to be disengaged completelyand immediately when a forward drivecondition is to be established from idling. The friction clutch includesa flywheel which is made up of cooperating main and subsidiary drivingplates which are normally spaced from each other by suitable springmeans. The subsidiary driving plate is positively moved away from thefrictionengaging plate when the clutch pedal is depressed and the clutchspring is moved to disengage the pressure plate from thefriction-engaging plate.

5 Claims, 2 Drawing Figures FRICTION CLUTCH The invention is concernedwith friction-engaging devices and, more particularly, it relates tofriction clutches of the dry-disc type having a friction-engaging platewhich can be clamped between a driving member such as a flywheel and apressure plate axially movable relative to the driving member. Thefriction-engaging device or the friction clutch herein disclosed isspecifically adapted for being incorporated in a motor vehicle powertransmission system of the counter-shaft type in which power deliveredfrom an engine-crankshaft is selectively transmitted to main and counterdrive shafts through coupling of the friction-engaging device or clutch.

The dry-disc friction clutches which are usually employed in the motorvehicle power transmission systems generally use a flywheel rotatablewith the engine crankshaft and a pressure plate drivingly connected tothe flywheel so that a driven element interposed between the flywheeland the pressure plate engages with the flywheel whereby drive torque istransmitted from the engine crankshaft to transmission input shaft. Thisdriven element is usually a friction-engaging plate secured to a clutchhub which is splined or keyed to the transmission input shaft and isfriction-engageable with a back face of the flywheel and a front face ofthe pressure plate. The pressure plate is biased to a position in whichthe friction-engaging plate is held in frictionengagement with theflywheel. When a clutch pedal for the transmission system is depressed,the pressure plate is retracted from the friction-engaging plate so thatthe friction-engaging plate is disengaged from the flywheel, therebyinterrupting the power through the clutch. It is, in this instance,important that, when the pressure plate is released from thefriction-engaging plate, then the friction-engaging plate be completelyand immediately free from contact with the flywheel so that no drivetorque is transmitted to the transmission input shaft.

Where the friction clutches of the above described construction areincorporated in the motor vehicle power transmission systems of thecounter-shaft type, a difficulty is sometimes encountered in that smoothsliding engagement between the transmission input shaft and the clutchhub supporting the frictionengaging plate is impaired especially afterthe clutches have been used for an extended period of time. This causesthe friction-engaging plate to fail to completely and immediatelywithdraw from the flywheel with the result that the transmission of thedrive torque is continued even when the clutch pedal is in a depressedcondition. A number of attempts have therefore been made so as toeliminate the difficulty of this nature, none of such attempts havingproved successful.

The power transmission system of the counter-shaft type hasa main drivegear formed at an end of the transmission input shaft and a counter gearformed on the counter-shaft and in constant mesh with the main drivegear. The main drive gear is usually a left-hand helical gear while thecounter gear is a right-hand helical gear. When, therefore, thetransmission system is shifted from idling to forward drive condition,an axial thrust is imparted to that transmission input shaft bycontinuous action along the helices of mating teeth of the two helicalgears. This axial thrust acts upon the transmission input shaft, which,as a result, is urged or actually moved toward the engine crankshaft.If, in this condition, the transmission input shaft fails to freelyslide on the clutch hub to which-it is splined, then thefriction-engaging plate supported by the hub tends to move toward theflywheel. Rotation of the flywheel is thus objectionably transmitted tothe friction-engaging plate and accordingly to the transmission inputshaft even though the pressure plate is held in its retracted position.

Such'problems will be solved if the helical main drive and counter gearsof the transmission system are substituted for usual spur gears so thatno axial thrust is imparted to the transmission input shaft. The use ofthe spur gear, however, creates other important problems such as thedegraded durability and generation of noises and, as such, arepractically acceptable. The above-noted problem will also be solved ifthe directions of the helix angles of the helical gears are inversed,viz., if the main drive gear is a right-hand helical gear and thecounter gear is a left-hand helical gear. In this instance,,the axialthrust resulting from the rotation of the helical gears is imparted. tothe transmission input shaft in a reversed direction, viz., toward themain drive shaft or away from the: engine crankshaft so thatdifficulties are now encountered in how to bear the axial thrust withinthe overall structure of the power transmission system. In order thatthis axial thrust to borne within the power transmission systemstructure in a satisfactory condition, the power transmission system ofthe counter-shaft type presently in common use will require extensiveand somewhat drastic changes and modification.

It is, therefore, an important object of this invention to provide animproved friction-engaging device, such as a friction clutch for motorvehicle power transmission systems, which can be completely and reliablydisengaged when it is desired to have the delivery of the drive torqueinterrupted therethrough.

It is another important object of the invention to provide an improveddry-disc friction clutch which is specifically adapted for use in motorvehicle power transmission systems of the counter-shaft type.

It is a further important object of the invention to provide an improveddry-disc friction clutch for the counter-shaft power transmission systemusing usual helical gears for transmitting the drive torque from thetransmission input shaft to the counter-shaft, which clutch is capableof being disengaged immediately and completely when the clutch pedal forthe transmission system is depressed during idling so as to establishforward drive condition.

It is a still further important object of the invention to provide animproved dry-disc friction clutch for the described motor vehicle powertransmission systems, wherein the driven member or friction-engagingplate can be disengaged from the engine flywheel completely andimmediately when the pressure plate is retracted therefrom even thoughthefriction-engaging plate is moved toward the flywheel due to thedeteriorated sliding engagement between the transmission input shaft andthe clutch hub splined thereto.

These and other objects of this invention can be accomplishedeconomically in a friction-engaging device which basically comprisessubstantially concentrically aligned, relatively rotatable membersincluding a main driving plate, a subsidiary driving; plate connected toand substantially spaced from the main driving plate, the subsidiarydriving plate being axially movable toward the main driving plate, apressure plate positioned at a spacing from the subsidiary drivingplate, at least one friction-engaging plate positioned intermediatebetween and engageable with the subsidiary driving plate and thepressure plate, and a cover member which is fast at its edge on thesubsidiary driving plate; first spring means positioned between thepressure plate and the cover member and having a neutral positionbiasing the subsidiary driving plate and cover member toward each otherto force the friction-engaging plate into engagement therebetween; andsecond spring means interposed between the main and subsidiary drivingmember for biasing the subsidiary driving plate toward the pressureplate through the friction'engaging plate. The second spring means maybe a diaphragm spring and/or a compression spring and is adapted to becompressed when the subsidiary driving plate is forced toward the maindriving plate when the coned disc spring is retracted from the neutralposition so that the pressure plate is caused to withdraw from thefrictionengaging plate whereby the power train through thefriction-engaging plate is destroyed.

Where the friction-engaging device thus constructed is used as afriction clutch for a motor vehicle power transmission system of thecounter-shaft type, the main and subsidiary driving plate constitutes,in combination, an engine flywheel and, as such, is rotated togetherwith the engine crankshaft. In this instance, the

friction-engaging plate is secured to a clutch hub which is splined orkeyed or otherwise axially movably mounted on the transmission inputshaft. The coned disc spring is associated with a clutch release meanssuch as a clutch release bearing which is axially slidable over thetransmission input shaft and which is operatively connected to a clutchpedal through a suitable mechanical linkage including, for instance, aclutch release fork or withdrawal lever, as customary.

Other features and advantages of the frictionengaging device or, in amost practical form, the drydiscfriction clutch in accordance with thisinvention will become more apparent from the following detaileddescription with reference to the accompanying drawing in which:

FIG. 1 is a longitudinal sectional view showing a preferred embodimentof the device according to the invention; and

FIG. 2 is a fragmentary view showing essential parts of anotherpreferred embodiment of the device according to the invention.

Referring now to FIG. 1, the friction clutch according to this inventionas shown forms part of a motor vehicle power transmission system of thecounter-shaft type which includes a crankshaft l driven from a motorvehicle engine, not shown, and a transmission input shaft 11 having .apilot end portion lla extending into an axial bore a in the crankshaft10. The transmission input shaft 11 is rotatable relative to thecrankshaft 10 through a pilot bearing 12. A flywheel 13 as a maindriving plateis connected to the crankshaft 10 through a bolt 14 or anyother fastening means. A generally annular member 15 as a subsidiarydriving memher is connected to the flywheel 13 through a guide pin 16 insuch a manner that the annular member 15 is movable toward and away fromthe flywheel 13. A diaphragm spring 17 is interposed between theflywheel 13 and annular member 15 so that the annular member is biasedto be spaced a distance d from the flywheel when the clutch is in acoupled position which is illustrated.

A clutch hub 18 having a radial extension or flange rivetted 18a isaxially interally splinded to engage external splines 19 on thetransmission input shaft 11 so as to be axially movable on the shaft 11.This clutch hub 18 supports thereon a friction-engaging plate which isgenerally designated by reference numeral 20. This friction-engagingplate 20 is usually made up of clutch disc mounts 21 and 21 which arefast on both faces of the flange portion of the clutch hub 18, a clutchdisc or cushioning plate 22 radially extending from the clutch discmount 21, and a pair of clutch friction facings 23 and 23 which arerivettpd or bonded to the cushioning plate 22. These friction facings 23and 23 are usually in an annular form and one of them, which is shown asthe facing 23, is so positioned as to be friction-engageable with theannular member or subsidiary driving plate 15 when the friction-engagingplate 20 is held in an operative position illustrated in FIG. 1.Designated by reference numeral 24 is a vibration damper which include acoil spring received within the flange portion 18a of the hub' 18 anddisposed in openings in the clutch disc mounts 21 and 21, as usual.

A pressure plate 25 is located adjacent the frictionengaging plate 20 ina manner to be engageable with the friction facing 23' of the plate 20.This pressure plate 25 is mounted on an axially movable clutch cover 26through a bolt 27, the clutch cover thus containing therein thefriction-engaging plate 20 and pressure plate 25, as shown. The clutchcover 26 is secured at its edge to the annular member 15 through a bolt28 so as to be rotatable therewith.

A coned disc spring 29 is located to be intermediate between thepressure plate 25 and the radial wall portion of the clutch cover 26 andsecured to the clutch cover through a thrust rivet 30 which is loaded bythrust rings 31 and 31'. This coned disc spring 29 has its outerperipheral edge seated on the back face, shown as protruded as at 25a,of the pressure plate 25 and its inner peripheral edge surrounding thetransmission input shaft 1 1, as illustrated. The coned disc spring 29thus biases the pressure plate 25 toward the annular member 15 so thatthe friction-engaging plate 20 is pressed against and rotatable with theannular member whereby the rotation of the crankshaft 10 is transmittedto the transmission input shaft 11 through the friction-engaging plate20. The coned disc spring 29 is associated with a clutch releasemechanism, generally designated by numeral 33, which usually includes aclutch release bearing, not designated, mounted over the transmissioninput shaft 11 and a withdrawal level operated by a clutch pedal, notshown, so as to move the clutch release bearing toward and away from thedisc spring 29, as usual. The transmission input shaft 11 is operativelyconnected at its leading end portion with main and counter drive shaftsthrough a transmission synchronizer and a gearing, respectively. Thisgearing includes a main drive gear formed on the transmission inputshaft and a counter gear formed on the counter shaft and in constantmesh with the main drive gear. Themain and counter drive gears areleft-hand and right-hand helical gears, respectively, as previouslynoted.

When, now, the clutch pedal is depressed and consequently the clutchrelease bearing is caused to press upon the coned disc spring 29, thenthe disc spring is moved or deformed to the position indicated by brokenlines so that the pressure plate 25 is freed from the spring action andretracted from the friction-engaging plate 20. Concurrently, the clutchcover 26 is moved or deformed in a manner to urge the annular member 15toward the flywheel 13 from which it has been spaced the distance d. Theresult is that the annular member of subsidiary driving plate 15 isforced toward the flywheel 13 against the spring action exerted by thediaphragm spring 17, thereby facilitating the frictionengaging plate 20to be disengaged from the annular member 15. As already described, whenthe transmission system is to be shifted from idling to the forwarddrive condition, the transmission input shaft 11 is urged toward thecrankshaft by reason of the axial thrust exerted thereto by the rotationof the helical main and counter drive gears. The friction-engaging plate20 is then also forced toward the annular member if smooth sliding ofthe clutch hub 18 on the shaft 11 is difficult due to wear of thesplines, accumulation of dust or the like. Even in this case, the clutchcan be uncoupled completely and immediately by the constructionaccording to the invention as described.

I FIG. 2 shows another embodiment of the device according to theinvention, in which a compression spring 32 is interposed between theflywheel 13 and annular member 15 in addition to the diaphragm spring17. In this instance, the diaphragm spring 17 may be removed so that thespring action between the flywheel 13 and annular member 15 is exertedsolely by the compression spring 32.

It will now be appreciated from the foregoing description that thefriction-engaging device according to this invention is characterized inthat flywheel assembly is made up of two members such as the main andsubsidiary driving plates 13 and 15 and that suitable spring means suchas the diaphragm spring 17 and/or compression spring 32 is interposedbetween these two driving plates so as to prevent improper or retardeddisengagement of the friction clutch otherwise caused when the forwarddrive condition is to be established from idling.

Although the friction-engaging device or friction clutch embodying thisinvention has been shown and described as being of the single-disc type,the features resulting from the invention are applicable to the frictionclutches of the multiple disc type.

What is claimed is:

l. A friction-engaging device comprising a rotatable main driving plate,a subsidiary driving plate connected to and spaced from said maindriving plate and movable relative thereto, a pressure plate spaced fromsaid subsidiary driving plate, at least one rotatable frictionengagingplate disposed between and engageable with said subsidiary driving plateand said pressure plate, and an axially movable cover member connectedto said subsidiary driving plate and said pressure plate, first springmeans positioned between said pressure plate and said cover member andhaving a neutral position for biasing said cover member and saidpressure plate toward said subsidiary driving plate thereby forcing saidfriction-engaging plate into engagement with said pressure plate andsaid subsidiary driving plate; second spring means interposed betweensaid main driving plate and said subsidiary driving plate for biasingsaid subsidiary driving plate away from said main driving plate; and anactuatable release mechanism engageable with said first spring means formoving said first spring means from said neutral position when actu atedwhereby said pressure plate and said subsidiary driving plate aredisengaged from said frictionengaging plate.

2. A friction-engaging device according to claim 1, in which said secondspring means comprises a diaphragm spring.

3. A friction-engaging device according to claim 1, in which said secondspring means comprises a compression spring.

4. A friction-engaging device according to claim 1, in which said secondspring means comprises a diaphragm spring and a compression spring. 7

5. in a motor vehicle having an engine crankshaft and a powertransmission of the counter-shaft type having an input shaft, and afly-wheel connected to and rotatable with the engine crankshaft, afriction clutch for coupling said engine crankshaft to said transmissioninput shaft comprising an annular member connected to and spaced fromsaid flywheel and movable relative thereto, a pressure plate spaced fromsaid annular member, at least one friction-engaging plate disposedbetween and engageable with said annular member and said pressure plate,a clutch hub axially movable along said transmission input shaft andsupporting said fric-' tion-engaging plate, an axially movable clutchcover connected to said annular member and said pressure plate andaxially movable toward. and away from said flywheel, first spring meansdisposed between said pressure plate and said clutch cover and having aneutral position in which said annular member and said clutch cover andsaid pressure plate are biased toward each other thereby forcing saidfriction-engaging plate into friction engagement with said annularmember and said pressure plate, second spring means interposed betweensaid flywheel and said annular member for biasing the annular memberaway from the flywheel, and an actuatable clutch release mechanismengageable with said first spring means for moving said first springmeans from said neutral position when actuated whereby said pressureplate and said annular member are disengaged from said friction-engagingplate.

1. A friction-engaging device comprising a rotatable main driving plate,a subsidiary driving plate connected to and spaced from said maindriving plate and movable relative thereto, a pressure plate spaced fromsaid subsidiary driving plate, at least one rotatable friction-engagingplate disposed between and engageable with said subsidiary driving plateand said pressure plate, and an axially movable cover member connectedto said subsidiary driving plate and said pressure plate, first springmeans positioned between said pressure plate and said cover member andhaving a neutral position for biasing said cover member and saidpressure plate toward said subsidiary driving plate thereby forcing saidfriction-engaging plate into engagement with said pressure plate andsaid subsidiary driving plate; second spring means interposed betweensaid main driving plate and said subsidiary driving plate for biasingsaid subsidiary driving plate away from said main driving plate; and anactuatable release mechanism engageable with said first spring means formoving said first spring means from said neutral position when actuatedwhereby said pressure plate and said subsidiary driving plate aredisengaged from said frictionengaging plate.
 2. A friction-engagingdevice according to claim 1, in which said second spring means comprisesa diaphragm spring.
 3. A friction-engaging device according to claim 1,in which said second spring means comprises a compression spring.
 4. Afriction-engaging device according to claim 1, in which said secondspring means comprises a diaphragm spring and a compression spring. 5.In a motor vehicle having an engine crankshaft and a power transmissionof the counter-shaft type having an input shaft, and a fly-wheelconnected to and rotatable with the engine crankshaft, a friction clutchfor coupling said engine crankshaft to said transmission input shaftcomprising an annular member connected to and spaced from said flywheeland movable relative thereto, a pressure plate spaced from said annularmember, at least one friction-engaging plate disposed between andengageable with said annular member and said pressure plate, a clutchhub axially movable along said transmission input shaft and supportingsaid friction-engaging plate, an axially movable clutch cover connectedto said annular member and said pressure plate and axially movabletoward and away from said flywheel, first spring means dIsposed betweensaid pressure plate and said clutch cover and having a neutral positionin which said annular member and said clutch cover and said pressureplate are biased toward each other thereby forcing saidfriction-engaging plate into friction engagement with said annularmember and said pressure plate, second spring means interposed betweensaid flywheel and said annular member for biasing the annular memberaway from the flywheel, and an actuatable clutch release mechanismengageable with said first spring means for moving said first springmeans from said neutral position when actuated whereby said pressureplate and said annular member are disengaged from said friction-engagingplate.